Bacterial cells, such as E. coli, are commonly used for producing recombinant proteins that do not require glycosylation. There are many advantages to using bacterial cells, such as E. coli, for producing recombinant proteins, particularly due to the versatile nature of bacterial cells as host cells, allowing gene insertion via plasmids. E. coli has been used to produce many recombinant proteins including human insulin.
Despite the many advantages to using bacterial cells to produce recombinant proteins, there are still significant limitations, including poor cell health phenotype.
Accordingly, there is still a need to provide new bacterial strains which provide advantageous means for producing recombinant proteins.
The generation of humoral and cell-mediated immunity is orchestrated by the interaction of activated helper T cells with antigen-presenting cells (“APCs”) and effector T cells. Activation of the helper T cells is not only dependent on the interaction of the antigen-specific T-cell receptor (“TCR”) with its cognate peptide-MHC ligand, but also requires coordinate binding and activation by a number of cell adhesion and costimulatory molecules.
The natural receptor binding to CD40 is CD40 ligand (CD40-L=CD154), a critical costimulatory molecule that is expressed on the surface of CD4+ T cells in an activation-dependent, temporally-restricted manner. CD154 is also expressed, following activation, on a subset of CD8+ T cells, basophils, mast cells, eosinophils, natural killer cells, B cells, macrophages, dendritic cells and platelets. CD40 is constitutively and widely expressed on the surface of many cell types, including B cells and other antigen-presenting cells.
Signaling through CD40 after engagement with CD154 initiates a cascade of cellular events that results in the activation of the CD40 receptor-bearing cells and optimal CD4+ T cell priming. More specifically, the binding of CD154 to CD40 promotes the differentiation of B cells into antibody-secreting cells and memory B cells.
The pivotal role of CD154 in regulating the function of both the humoral and cell-mediated immune response has provoked great interest in the use of inhibitors of this pathway for therapeutic immunomodulation. As such, anti-CD154 antibodies have been shown to be beneficial in a wide variety of models of immune response to other therapeutic proteins or gene therapy, allergens, autoimmunity and transplantation (see, e.g., U.S. Pat. No. 5,474,771 and WO 2008/118356, which are incorporated herein by reference in their entirety).
There is a need in the art to efficiently and cost-effectively produce high amounts of antibodies or antibody fragments interfering with the interaction of CD40 and CD154 suitable for therapeutic applications.